The invention relates to a coplanar patch antenna including a continuous layer of dielectric material, a patch of conductive material supported on a major surface of the layer of dielectric material, a ground plane of conductive material supported on said major surface of the layer of dielectric material and substantially surrounding and spaced from the patch of conductive material, and means for feeding electrical signals to the antenna. A form of coplanar patch antenna of the kind specified is disclosed in an article "Coplanar Stripline Antenna" by John W. Greiser in Microwave Journal, October, 1976, pages 47 to 49, and in U.S. Pat. No. 4,063,246. In the disclosure, the conducting patch is connected directly to the strip conductor of a coplanar stripline formed in the ground plane supported on the first mentioned major surface of the dielectric layer, and a further ground plane is supported on the other major surface, the dielectric layer being relatively thin so that the further ground plane is in the fringing field between the strip conductor and the first-mentioned ground plane.
This arrangement has an inconveniently high feedpoint resistance of about 400 ohms.